Method and device for positional determination of user appliances in a radio communication system using additional positional elements in neighboring radio cells

ABSTRACT

A method and system are provided for positional determination of at least one user appliance in a radio communication system, which includes a number of base stations for dividing into radio cells, in which at least one localization measuring signal is transmitted by at least one positional element from at least one radio cell adjacent to the radio cell in which the user apparatus is located.

BACKGROUND OF THE INVENTION

The present invention relates to a method for determining the positionof at least one subscriber device of a radio communication system whichhas a number of base stations respectively associated with a number ofradio cells, with at least one locating measuring signal beingtransmitted by at least one additional position element.

In radio communication systems, such as, for example, those according tothe GSM or UMTS standard, it may, if appropriate, be of interest todetermine the current location of a specific subscriber device; inparticular, a mobile radio device. The requirement of the position ofthe respective subscriber device to be determined may arise from therespective subscriber himself/herself, from another subscriber or fromthe network infrastructure side.

SUMMARY OF THE INVENTION

The present invention, therefore, is directed toward a method and systemin which the position of the respective subscriber device in a radiocommunication system can be determined as efficiently as possible. Thisis achieved in a method of the type mentioned at the beginning, and inan associated system, by virtue of the fact that at least one locatingmeasuring signal is transmitted by at least one position element from atleast one radio cell which is adjacent to the radio cell in which thesubscriber device to be respectively located is present, and is used todetermine the position of the subscriber device in the radio cell inwhich it is located at that particular time. As a result of the factthat in each case at least one locating measuring signal is transmittedby at least one position element in one or more neighboring radio cells,it is not necessary for position elements to be additionally provided inthe radio cell in which the actual subscriber device to be located ispresent at that particular time. This permits effective utilization ofany position elements which are already present. Supplementaryapplications for the radio network infrastructure can thus be dispensedwith.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of a number of radio cells of a radiocommunication system in which the position of a mobile radio devicewhich is to be located can be determined according to a first embodimentof the method according to the present invention only using positionelements in radio cells which are adjacent to the radio cell in whichthe mobile radio device to be located is present at that particulartime.

FIG. 2 is a schematic view of a radio cell of a radio communicationsystem in which position elements arranged in the radio cell can be usedin a known fashion to determine the position of a mobile radio devicewhich is located therein.

FIG. 3 is a schematic view of a second embodiment of the methodaccording to the present invention for determining the position of asubscriber device of the radio communication system according to FIG. 1.

FIG. 4 is a schematic view of the further components of the radiocommunication system according to FIG. 1.

FIG. 5 is a schematic view of the chronological structure of a timeframe of the radio signaling on the air interface between a base stationand a subscriber device, to be located, of the radio communicationsystem according to the present invention, in accordance with FIGS. 1and 3, with a locating measuring signal from at least one positionelement of at least one of the adjacent radio cells having been insertedinto this free signal section of a time slot of this time frameaccording to the method of the present invention.

Elements with the same functioning and method of operation arerespectively provided with the same reference symbols in FIGS. 1 to 5.

DETAILED DESCRIPTION OF THE INVENTION

The functional components of a cellular radio communication system MCSare illustrated schematically in FIG. 4, in which telecommunicationsignals are transmitted via at least one predefined air interface (LS1)between at least one subscriber device, in particular a mobile radiodevice such as, for example, UE1, and at least one base station such as,for example, NB, SB using a time-division multiplex multiple-accesstransmission method. The system is preferably embodied as a mobile radiosystem according to the UMTS (Universal Mobile Telecommunication System)standard. Here, telecommunication signals are transmitted via therespective air interface, in particular in accordance with a combinedTDMA/CDMA multiple-access transmission method (TDMA=Time DivisionMultiple Access; CDMA=Code Division Multiple Access). In particular, itis operated in what is referred to as the TDD (Time Division Duplex)mode. In the TDD mode, a separate signal for transmission is broughtabout in the uplink and downlink directions (Uplink=signal transmissionfrom the mobile radio device to the respective base station,Downlink=signal transmission from the respectively assigned base stationto the mobile radio device) via a corresponding, separate allocation oftime slots using a time-division multiplex method. Here, preferably onlya single carrier frequency is used for signal transmission in the uplinkand downlink directions. In order to be able to bring about subscriberseparation, the telecommunication signals are, expressed in simpleterms, divided over time into a number of successive time slots with apredefinable time period with a predefinable time frame structure duringthe radio transmission via the air interface of the respectivesubscriber device to the assigned base station (and visa versa). Anumber of subscribers, which communicate simultaneously in the sameradio cell with the respectively associated base station, are separated,in combination with the time multiplex division, from one another interms of their telecommunication/data connections via orthogonal codes;in particular, using what is referred to as the CDMA (Code DivisionMultiple Access) method.

The subscriber devices provided are preferably mobile radio telephones;in particular, mobile phones. In addition, it is also possible for othertelecommunication and/or data transmission devices with assigned radiounit (transmitter and/or receiver unit) such as, for example, aninternet computer, television sets, notebooks, fax machines, etc., to beembodied for “on air” communications traffic (i.e., via an airinterface), and for them to be components of the radio communicationnetwork. The subscriber devices may, if appropriate, also be arrangedhere in a stationary, or fixed, fashion in the radio network.Preferably, they also may be of portable design and thus can be mobile;i.e., be used in different locations.

The cellular mobile system MCS usually has a number of base stationswhich are each assigned mobile radio cells; i.e., each base stationproduces one radio cell and supplies it, in terms of radio traffic, viaat least one air interface. Within such a radio cell, its base stationis therefore respectively responsible for communication with asubscriber device which is respectively present therein. The respectivebase station is preferably arranged approximately in the center of itsradio cell.

Here, in the exemplary embodiment in FIG. 4, only two base stations NB,SB are shown for the sake of clarity, the base stations beingrepresentative of the number of other base stations which are present inthe radio network. A subscriber device UE1 which is to be located ispresent in the radio cell of the base station SB. In particular, thesubscriber device UE1 (User Equipment) expressed in general terms, is aphysically mobile, (i.e., portable) terminal, for telecommunication. Abase station is in each case a network component which serves and, ifappropriate, monitors mobile terminals in a mobile radio cell of atleast one air interface.

The base station SB in FIG. 4 is that network component which iscurrently serving and monitoring the mobile terminal UE1 to be locatedin the radio cell in which it is present at that particular time; i.e.,a serving mobile radio cell), via the air interface LS. The basestations such as, for example, NB, SB can in turn be combined intogroups and connected via a fixed network connection Iub to a subordinatenetwork unit SRNC (Serving Radio Network Controller) which, using aprotocol RRC (Radio Resource Control=protocol for transmitting messagesbetween a mobile subscriber device and Serving Radio NetworkController), organizes and monitors the communication/data trafficbetween the respective mobile subscriber device and the respectivelyassigned base station. What is referred to as a Serving Radio NetworkController is, therefore, a network component for serving and monitoringone or more base stations which are called NodeBs in UMTS. Therespective Serving Radio Network Controller and the base stationsassigned to it form what is referred to as a Radio Network System (RNS).

A number of RNS systems are, in turn, combined in UMTS to form a logicsystem unit UTRAN (Universal Terrestial Radio Access Network). Theswitching unit 3GMSC (3rd Generation Mobile-services Switching Center)establishes the interface between the radio system MSC and fixednetworks such as, for example, PLMN (Public Land Mobile Network) via afixed link Iu. The MSC carries out all the necessary functions relatingto this for circuit switched services from and to the mobile stations. Acommunications link for an external location application (e.g., positiondetermining) or an external location client (LCS client) is madepossible via a connection unit GMLC (Gateway Mobile Location Center).This connection unit GMLC is connected to what is referred to as a “HomeLocation Register” HLR to which a mobile user is assigned for protocoland monitoring purposes (e.g., user information). An external locatingunit such as, for example, a LCS client ELCS (location services)application system (e.g., emergency call centers, monitoring centers,position-dependent information services) can enter into contact with theradio communication system MCS via the connection unit GMLC.

In the traffic state which is given by way of example in FIG. 4, themobile radio device UE1 has already set up an active, existingcommunication link to the base station SB in the radio cell in which itis located at that particular time. As a result, telecommunicationsignals or data signals can be transmitted both from the base station SBto the mobile radio device UE1 (=downlink) and from the mobile radiodevice UE1 to the base station SB (=uplink). An evaluation/arithmeticunit AE (shown by dot dashed lines) is connected to the base station SBusing network elements which are not shown in FIG. 4 for the sake ofclarity. The unit AE can be used to carry out the calculation ordetermination of positions (PCF=Position Calculating Function) of themobile radio device UE1 on the basis of the measurement data. Thisevaluation/calculation unit AE also may be implemented as a component ofthe respective base station and/or in the mobile radio device UE1itself.

According to one mobile radio standard of the third generation, such asUMTS (see WCDMA for UMTS—Radio Access for Third Generation MobileCommunications: H. Holma, A. Toskala; John Wiley & Sons, New York; ISBN0-47172-051-8; 2000), the position of a mobile radio device can bedetermined using the support of what are referred to as positionelements. More details on this are given in 3G TSGR1#8(99)g57:Positioning method proposal, PANASONIC, New York (USA), TSG RAN1Meeting#8, 12–15.10.1999, 3G TSGR2#8(99)e48: Positioning methodproposal, PANASONIC, Cheju (Korea), TSG RAN2 Meeting#8, 2–5.11.1999 and3G TSGR2#15-R2-001718: Assessment procedure for the OTDOA-PE positioningmethod, PANASONIC, Sophia Antipolis (France), TSG RAN2 Meeting#15,21–25.8.2000.

FIG. 2 shows, by way of example, the radio cell CE1 from the number ofradio cells of the radio communication system according to FIG. 4. Thisindividual radio cell CE1 is supplied, in terms of radio equipment, bythe approximately centrally arranged base station NB1. Expressed ingeneral terms, in a cellular mobile radio system such as, for example,UMTS, base stations or NodeBs produce associated, individually assignedmobile radio cells. Within a mobile radio cell, a subscriber device canhave a radio link to the base station which produces this cell. A numberof other radio cells are thus adjacent to the respective radio cell suchas, for example, CE1, the radio cells each being produced by anindividual base station. These have been omitted in FIG. 2 for the sakeof simplicity. In order to be able to determine the position, orlocation, of the mobile radio device UE1 which is present in the radiocell CE1 at a given time, in each case one or more position elementssuch as, for example, PE11 to PE14 are additionally arranged distributedin the respective individual radio cell such as, for example, CE1itself.

The position elements are preferably placed in the region of theexternal boundaries of the radio cell CE1. In order to determine theposition of the mobile radio device UE1, on the one hand, the basestation NB1 itself transmits, via its air interface LS1, one or morelocating measuring signals whose transit time is measured for itstransit path to the mobile radio device UE1, and determines therefrom adistance circle RTK1 around the base station NB1 as a center point (whatis referred to as RTT (round trip time) measurement). The mobile radiodevice UE1 is located on this circle RTK with a constant radius. On theother hand, in order to further delimit its location, one or morelocating measuring signals are transmitted simultaneously, or eachoffset chronologically by a known time period, by at least two furtherposition elements such as, for example PE1 and PE3. At least two furtherdistance circles CI1 and CI3 are determined via the mobile radio deviceUE1, using corresponding transit time measurements of these locatingmeasuring signals. Here, the distance circle CI1 characterizes thoselocations at which a locating measuring signal of the position elementPE1 has in each case, the same transit time for its transit path to themobile radio device UE1. The distance circle CI2 describes thoselocations at which a locating measuring signal of position element PE2has, in each case, the same transit time for its transit path to themobile radio device UE1. Only the point of intersection of all threedistant circles RTK1, CI1, CI2 gives the location of the mobile radiodevice UE1 unambiguously.

The position elements PE11 to PE14 are expediently synchronized withrespect to the timing pattern of the radio signaling on the airinterface LS1 of the base station NB1. This is because, in this way, thestarting time of the locating measuring signals of the position elementsis defined unambiguously, which facilitates the evaluation of thetransit times of the locating measuring signals.

Instead of the distance circles RTK1, CI1, CI2 and/or in combinationwith them, it is also possible to determine local hyperbolas on thebasis of the transit time of the locating measuring signals, as in whatis referred to as the OTDOA (Observed Time of Arrival) method. Moredetails on this known OTDOA position element measuring method(OTDOA=Observed Time Difference of Arrival) can be found in 3GTSGR1#8(99)g57: Positioning method proposal, PANASONIC, New York (USA),TSG RAN1 Meeting#8, 12–15.10.1999, 3G TSGR2#8(99)e48: Positioning methodproposal PANASONIC, Cheju (Korea), TSG RAN2 Meeting#8, 2–5.11.1999, 3GTSGR2#15-R2-001718: Assessment procedure for the OTDOA-PE positioningmethod, PANASONIC, Sophia Antipolis (France), TSG RAN2 Meeting#15,21–25.8.2000. The determination of the position in accordance with theOTDOA method is based, in particular, on measurement of signals of theair interface between a number of base stations (NodeBs) and/or positionelements in the respective radio cell in which a subscriber device ispresent, and the subscriber device which is to be respectively located.According to this method, the subscriber device which is to be locatedattempts to detect at least one pair of a known signal, for example fromtwo adjacent base stations at different locations, and/or positionelements within the respective radio cell in which a subscriber deviceis present. The reception times of the signal of two adjacent NodeBswhich are at different locations and/or position elements of the sameradio cell in which the subscriber device is present are then preferablytransmitted, for evaluation purposes, to the respective evaluation unitPCF (Position Calculation Function) of that base station (Serving NodeB)which is responsible for the subscriber device to be located. Evaluationrefers to the PCF forming the difference between the reception times ΔT.This ΔT describes a hyperboloid which specifies that the location inwhich the subscriber device to be located is present is on a hyperbola(see Taschenbuch der Mathematik: I. N. Bonstein, K. A. Semendjajew, G.Musiol, H. Muhlig; Verlag [publishing house] Harri Deutsch; 4th edition:1999). As a result of at least one further adjacent base station and/orone further position element of the same radio cell in which asubscriber is present being included, the location in which thesearched-for subscriber device is present is, thus, on one of the twopoints of intersection of two hyperbolas. A further item of informationis also necessary for an unambiguous determination position. Forexample, it is possible either:

a) to determine an OTDOA measurement with respect to a fourth NodeBand/or with respect to a further position element of the same radio cellin which the subscriber device is present (results in a thirdhyperbola); and/or

b) in cells with sectorization, the information relating to the sectorin which the subscriber device is located can be used to arrive at adecision; and/or

c) an RTT measurement can be carried out.

The locating measuring signal which is to be respectively detected maybe the signal of what is referred to as the CPICH (Common Pilot Channel)which is continuously transmitted by the NodeBs. In order to distinguishbetween the CPICH signals, each NodeB and/or each position element isexpediently assigned a different spread code. As such, it is possible todifferentiate the received CPICH signals, to assign them to thecorresponding NodeBs or position elements, and to calculate thenecessary time differences.

The synchronization of the NodeBs with one another also influences thecalculation of positions. Here, the PCF is informed whether the NodeBsare synchronized. If they are not, it is advantageous for thechronological shift which is present between the individual NodeBs to besignaled to the adjacent base stations. Possible chronological shiftswith respect to the transmission times can then be included in thecalculations for the sake of correct calculation processes. Thebackground to this is that, for the calculation of position, it is thuspossible to assume that the locating measuring signals from the variousbase stations have been output into the network at approximately thesame time. Using the OTDOA method, anaccuracy in the positiondetermination of the UE of approximately 80–100 m is preferablyobtained.

In an expansion of the OTDOA method for the case in which the signals ofthe NodeB which serves the UE overlap with the locating measuringsignals of the other NodeBs, in what is referred to as the OTDOA-IPDLmethod (Observed Time Difference of Arrival-Idle Period Downlink), thetransmissions of the NodeB (which are used by the UE which is to belocated—referred to as serving NodeB), are switched off for short timeperiods, IPDLs. Otherwise, a detection of the respective CPICH signal ofother NodeBs would in fact be made more difficult and even be impossibleover wide parts of the mobile radio cell. These additionally insertedpauses in relation to the transmission of this NodeB can then beutilized by the UE in order to detect the reception times of the CPICHsignals of the adjacent NodeB. This pause (idle period) may be severalsymbols long, generally 5–10 symbols. Here, the length of one symbolcorresponds, for example, in the FDD mode of UMTS to 256 chips, and inthe TDD mode to a max of 16 chips, 1 chip being approximately 0.26 μslong (given a chip frequency of 3.84 Mchips/s). Owing to theintroduction of the IPDLs and, thus, the deactivation of thetransmission of signals of the NodeB of interest, a capacity loss orinformation loss occurs in the corresponding mobile radio cell for thetime of the IPDLs. Using the OTDOA-IPDL method, an accuracy in thedetermination of position of up to approximately 20 m is obtained. Acorresponding procedure is also preferably adopted if position elementsare additionally used in the respective radio cell in which the deviceis present at that particular time.

The number of position elements is defined by the network operator inaccordance with the local conditions of the respective mobile radio celland the required accuracy of the determination of position for eachindividual radio cell. With the previous locating method, it is onlypossible with the PEs to use, for position-determining purposes, thesignals of only that mobile radio cell in which the mobile radio deviceto be determined is located at that particular time. Signals from otherNodeBs (in the adjacent mobile radio cells) for the OTDOA evaluation arebasically no longer necessary but can, of course, be used neverthelesswhen they are present and detected. The insertion of IPDLs is no longerabsolutely necessary, something which avoids the capacity loss of thecell which is mentioned in the OTDOA-IPDL method (see above).

Theoretically, in this method IPDLs also can increase inaccuraciesfurther. The PEs have two main functions:

a) they listen to the mobile radio cell traffic in the DL (down-link),to the transmission from the NodeB to the UEs; and

b) they each transmit a predefined signal code, assigned to each PE, tothe UEs in the DL.

The listening and transmitting are each carried out at a frequency, thedownlink frequency of the mobile radio cell (serving cell); for example,the frequency of the broadcast channel BCH. However, both operations, oflistening and transmitting, are separated from one anotherchronologically so that overlapping cannot and should not occur.

If a request for position determination of a subscriber device (UE) ispresent in a cell, the PEs which are respectively present in the mobileradio cell are informed by the serving NodeB (via higher signalinglayers or via the BCH), to transmit their assigned signal code in aspecific downlink slot (DL slot). The transmission takes place atspecific times and in specific, free signal sections of the DL slot ofthe transmission signal of the serving NodeB to the UEs; i.e., the PEsplace their uniquely defined signal code sequences in signal sections,predefined by the serving NodeB, of the signaling of the serving NodeBto the UEs of this mobile radio cell (see PS1 in FIG. 5). It ispossible, for example, for these to be signal sections of the BCH whichare not used by it or signal sections in the data parts such as, forexample, DA1 of a slot (time slot) such as, for example, SLi. The UEwhich is to be located is, of course, also aware of the signal sectionsin which the PEs transmit their signal codes. As a result, the UE canattempt, in accordance with the signaling time, to detect the signalcodes of the PEs in the specific part of the DL slot and in doing sodetermine the arrival times of the signal codes. The further procedureand determination of the position takes place in accordance with theOTDOA method specified above, according to FIGS. 2 and 4.

To summarize, the essence of this known position-determining method isthat one or more position elements (PE), with whose support positiondeterminations can be carried out according to the principle of theOTDOA method, are introduced per mobile radio cell. The number ofposition elements is defined by the network operator, preferably inaccordance with the local conditions (for example, topography) of therespective mobile radio cell and the required accuracy of the positiondetermining process.

With the PEs it is possible to use, for position-determining purposes,the signals of only that mobile radio cell in which the UE to bedetermined is present. Signals of other NodeBs (in the adjacent mobileradio cells) for the OTDOA evaluation are basically no longer necessary.However, they also can, of course, be used if they are present anddetected.

In the PE method which is described above, PEs can be introduced intoeach mobile radio cell. The decision in this respect is taken by themobile radio network operator. Various points are to be taken intoaccount here:

-   1) Number of the PEs in view of costs:    -   a) PEs are to be seen, depending on their method of operation,        as “slimmed down” or very simple mobile radio devices with the        minimum functions of listening to a frequency and transmitting a        fixed signal code into the mobile radio space at one frequency.    -   b) Despite “slimming down” (reduced functionality), the PEs        entail specific costs (procurement, energy consumption,        location).-   2) Use as a supplement to the NodeBs for covering only specific    regions with the PEs so that PEs possibly are not present in each    mobile radio cell but rather only in specific regions, for example:    -   a) Indoor areas    -   b) gaps between tall buildings    -   c) mountainous countryside-   3) geographic and/or legal conditions in the mobile radio cell; for    example, possible prohibition against installing PEs.

A further problem is the possible, if not proven, health risks of mobileradio waves in heavily populated areas or the like. For all theabovementioned reasons, it is acceptable or imaginable that PEs of thecellular radio communication network will not be present in each mobileradio cell. This could then have negative effects in terms of thedetermination of the position of one or more UEs and its accuracy in thethese mobile radio cells which are without position elements.

Despite these conditions (i.e., mixture of radio cells with and withoutadditional position element), it is possible to carry out thedetermination of the position of a subscriber device over a large areaby using the locating measuring signals of one or more position elementsin adjacent radio cells for evaluation in those radio cells in which noposition elements, or too few position elements, are present. In otherwords, use is made of PE elements in radio cells which are adjacent tothe radio cell in which the subscriber device to be respectively locatedis present at that particular time (but without support, or withinsufficient support by position elements in the radio cell (servingcell) in which the UE to be located is present at that particular time(see FIGS. 1 and 3). For the case just mentioned in which PEs are notpresent or there is an inadequate supply of PEs in the respectiveserving cell, one or more PEs are, therefore, stationed in one or moreadjacent cells and their locating measuring signals are used for thedetermination of position. As a result, such gaps in provision areclosed.

As the assignment of the maximum 240 signal codes (in particular, the240 unused S-SCH codes (Secondary Synchronization Channels); in UMTS, of256 channels made available only 16 are allocated and used) tocorresponding PEs of the mobile radio network is known in advance to theUEs via the BCH (transmitted by the NodeBs or the higher signalinglayers in the case of, for example, the first radio contact=logging on),it is possible for the UEs in the serving cell to listen to the signalcodes of the PEs from the adjacent cells.

The quintessence of the solution to the above problems is, inparticular, the use of position elements of the adjacent cells in theserving cell, or preferably via the uniquely defined signal codes whichare assigned to them and known in advance, for determining the positionof UEs in the serving cell. The determination of the positionadvantageously can be carried out here in accordance with the OTDOAmethod.

In this way, on the one hand, the costs of the network operators can bereduced by virtue of a smaller number of necessary position elements inthe radio communications network. Adverse effects in terms of theavailability and accuracy of the determination of position are thus,largely avoided. A further advantage is that failure times of PEs ofwhatever kind in the serving cell can be compensated using PEs in theadjacent mobile radio cells. Position calculations, therefore, continueto be possible. A main advantage is, in particular, the more effectiveplanning of the locations of the PEs. Associated with this are thealready-mentioned savings in PEs in the entire network. The locations ofthe PEs can be particularly selected such that, in the one mobile radiocell, PEs are located more toward the edge of the cell, and in theadjacent cells they are located more in the direction of NodeB or morein the direction of the local features which cause problems in terms ofthe geographic conditions (see FIG. 3). With the use of PEs from theadjacent mobile radio cells it is also possible to avoid, decrease orattenuate geographic, legal or health problems relating to theinstallation of PEs in some mobile radio cells.

With the present method it is possible to dispense with IPDLs (as in theOTDOA-IPDL method). As a result, the loss of capacity can be avoidedbecause of possible IPDLs. Therefore, it is possible for the networkoperator to reach his/her target capacity, even with the feature“determining the position of UEs.”

Exemplary Embodiment 1

In the first exemplary embodiment, FIG. 1 serves as a basis for theexplanations. It is assumed that, by way of example, four base stationsNB1, NB2, NB3 and NB4 cover the UMTS mobile radio cells CE1, CE2, CE3and CE4. Further adjacent cells will not have any role in the firstexemplary embodiment, for the sake of clarity. These NodeBs aremonitored and served by a RNC, thus giving rise to a system includingmonitoring element, base stations, mobile radio device and positionelements (the RNC is the superordinate monitoring unit for a specificnumber of NodeBs and is not explicitly specified in FIG. 1).

Furthermore it is assumed that a mobile radio device UE1 which is to belocated is present in the UMTS mobile radio cell CE1 (the serving cell)and is supplied or served by this base station or NodeB NB1. Here, it isnot relevant whether the interrogation as to the determination of theposition starts from the mobile radio device UE1 or from the networkand, thus, from any interrogating client in the network.

The hexagonal mobile radio cell which is shown in FIG. 1 represents anabstraction for the sake of better presentation of the arrangement of amobile radio cell and its elements.

Furthermore, a certain number of PEs are present in the adjacent mobileradio cells CE2, CE3 and CE4, while no position elements are positionedin the radio cell (serving cell) CE1 in which the device is present atthat given time. In detail, the additional position elements PE21, PE22are arranged in the adjacent radio cell CE2, the position elements PE31,PE32 in the adjacent radio cell CE3, and the position elements PE41,PE42 in the adjacent radio cell CE4. The PE distribution in the mobileradio cells CE2, CE3 and CE4 is performed in such a way that thelocating measuring signals of the PEs of these adjacent radio cells, inthis example the UMTS mobile radio cells CE2, CE3 and CE4, can besatisfactorily “heard” (i.e., detected), in the serving cell of thesubscriber device UE1 to be located. In general, this refers to the PEspreferably being stationed in the vicinity of the cell boundary, near tothe serving cell. Here, the distribution is preferably configured suchthat the locating measuring signals of all the PEs in total cover, asfar as possible, 100% of the UMTS mobile radio cell CE1 in which thedevice is located at that particular time.

If, for example, the subscriber device UE1 which is to be located ispresent in the mobile radio cell CE1 near to its upper left-hand corner,it is possible that the subscriber device UE1 can evaluate measurementsignals of the position elements PE21 and PE42 during a positioninterrogation. On the other hand, problems will and can occur withrespect to the detection of the locating measuring signals of the otherPEs (PE31, PE32, PE41) because these PEs are difficult for thesubscriber device UE1 to be located to detect, or cannot be detected atall. The reasons are the relatively large distances and, as a result,weaker signal powers and possibly a greater quantity of shadowing in thedistance between these PEs and the subscriber device UE1.

If the subscriber device UE1 is, according to FIG. 1, approximately inthe center of the right-hand half of the UMTS mobile radio cell CE1, itis possible for it to detect the signal code sequences of the positionelements PE21, PE31, PE32 and PE42 of the adjacent radio cells CE2, CE3,CE4 to a degree lying between satisfactory and very satisfactory, whilethe position element PE42 is already too far away for sufficiently goodreception. A possible sequence for the determination of the position ofthe subscriber device UE1 could be, by way of example, as follows:

The position of the subscriber device UE1 in the UMTS mobile radio cellCE1 is to be determined; it is not relevant here why there was aposition interrogation or where it came from. Owing to theposition-determining accuracy which is defined in the requirements, theRNC will decide to use position elements (PEs). After this, the basestation NB1 of the radio cell CE1 in which the device is present will beinformed by the RNC. Via the BCH, radio cell CE1 informs the PEs of theadjacent mobile radio cells, CE2, CE3 and CE4 of the positioninterrogation and the times at which the respective position elementinserts its signal code sequence, assigned to it, into the DL slotstructure of the NodeBs NB1 for the subscriber device UE1. In the firstinstance, the fact that the PEs are situated in the vicinity of the cellboundary of the UMTS mobile radio cell CE1, and thus also receive the DLtraffic, ensures that the position elements (PEs) in the adjacent cellsare provided with this information. In the second instance, the RNCensures that the adjacent NodeBs also integrate this information intotheir DL traffic. The subscriber device UE1 is also provided with thisinformation as the DL link of the serving nodeB NB1 also hears this. Atthe given times, the position elements PE21, PE31, PE32 and PE41 theninsert their signal code sequences into the respective DL slotstructure. The subscriber device UE1 then attempts to determinereception times of the code sequences using the knowledge of the signalcode sequences and of the associated position element (via, for example,a rake receiver (i.e., correlation receiver), with which time shifts canbe determined by correlations). This information is transmitted by thesubscriber device UE1 to the serving nodeB NB1. From this, nodeB NB1then determines time differences between the reception time points ofthe PE signal code sequences. These differences are mapped ontohyperbolas using the OTDOA method; the common point of intersection ofthe hyperbolas is the searched-for position in an accuracy value rangewhich is dependent on the surroundings.

Exemplary Embodiment 2

Exemplary embodiment 2 is related entirely and completely to the aboveexemplary embodiment 1 and relates to FIG. 3 instead of FIG. 7. Thedifference is the expansion to 6 UMTS mobile radio cells (CE1 to CE6),and the changed number of PEs and their assignment. There are now threeposition elements present: PE32 in UMTS mobile radio cell CE3, PE41 inUMTS mobile radio cell CE4, and PE61 in UMTS mobile radio cell CE6.There are no position elements in the UMTS mobile radio cells CE2 andCE5, or in the UMTS radio cell CE1 in which the device is present atthat particular time. Here, the following is to apply:

-   1) The position element PE61 (in UMTS radio cell CE6), PE41 (in UMTS    radio cell CE4), and PE32 (in UMTS radio cell CE3) together cover    the UMTS cell CE1 in terms of radio equipment.-   2) The position element PE61 (in UMTS radio cell CE6), PE41 (in UMTS    radio cell CE4), and PE32 (in UMTS radio cell CE3) also respectively    cover their own mobile radio cell to a certain extent.-   3) The position element PE61 (in UMTS radio cell CE6) additionally    covers the upper part of the UMTS radio cell CE5.-   4) The position element PE41 (in UMTS radio cell CE4) additionally    covers the lower part of the UMTS radio cell CE3 and UMTS radio cell    CE5.-   5) The position element PE31 (in UMTS radio cell 3) additionally    covers the lower part of the UMTS radio cell CE2.

The position of the subscriber device UE1 is determined in a way whichis analogous to the descriptions in exemplary embodiment 1. Exemplaryembodiment 2 is intended to clarify, in particular, that a differentnumber and arrangement of the position elements (PEs) does not result inany fundamental difference.

Exemplary Embodiment 3

Exemplary embodiment 3 relates entirely and completely to the twoprevious exemplary embodiments 1 and 2. The difference or the expansionis the use or introduction of pauses in the DL traffic of the NodeB NB1to the subscriber device UE1 to be located. In specific terms, thismeans: for the signal code sequences of the PEs of the adjacent UMTSmobile radio cells (CE2 to CE6 in FIG. 3) to be able to be detectedlargely without any disruptive influences of the NodeB NB1, the DLtransmission from the NodeB NB1 to the subscriber device UE1 is switchedoff for a specific time period, referred to as idle periods. All thecorresponding PEs then transmit their signal code sequences precisely inthis idle period. The information about the idle period is also providedvia the BCH channel. This thus increases the probability of thesubscriber device UE1 to be located detecting the corresponding PEs asfar as possible (i.e., as far as possible by 100%), and in addition,under certain circumstances, detecting signals from other, more distantPEs. The result would be a qualitatively better determination ofposition.

FIG. 5 shows in a schematic view the chronological structure of a timeframe FRi of the radio signaling on the air interface LSi between thebase station NB1 and the mobile radio device UE1 to be located, inFIG. 1. Here, in a free signal section of a time slot of this timeframe, a position element which is also listening in has inserted alocating measuring signal in one of the adjacent radio cells using themethod according to the present invention via either automatic selectionor defined assignment in advance. The time frame FRi of thechronological length TF has a number of individual, chronologicallysuccessive time slots SL0 to SL14 of respectively the same, constanttime period. Such time frames in such a context follow one another insuccession; i.e., continuously during the telecommunicationstransmission. This is indicated in FIG. 5 by, in each case, three pointsat the start and end of the time frame FRi. The structure of the timeframe FRi preferably corresponds to the slot structure of what isreferred to as a TDD frame (TDD=Time Division Duplex). A TDD frame suchas, for example, FRi is preferably composed here of a total of 15 timeslots SL0 to SL14. Here, each time slot can be allocated (i.e., reservedor made available), in a uniquely defined way either for transmissionsin the uplink traffic or downlink traffic.

FIG. 5 shows a schematic view of the chronological configuration or thestructure (i.e., the chronological division of a time slot) such as, forexample, SLi of the time frame FRi. Each respective time slot, such as,for example, SLi has 4 time sections DA1, MI, DA2, PC2 which arereserved for the transmission of various groups of signal types. Thefirst time section DA1 of the time slot SLi is preassigned for thetransmission of useful data, referred to as data symbols. Then, in thesecond, subsequent time section or block MI, what are referred to asmidambles are transmitted. These are signals for the channel estimationand/or synchronization of the respective subscriber device and/or of therespective base station. In particular channel equalization in therespective mobile radio device and/or the respective base station iscarried out on the basis of these channel estimation parameters. Thistime block MI is, in turn, followed by a time section DA2 for a furthertransmission of useful data. By virtue of the fact that the midambles ofa channel estimation are transmitted between the two blocks with theuseful data or useful signals, it is largely ensured that the respectiveradio channel can be equalized to an optimum degree when averaged overtime. During the fourth, last time section PC2 of the time slots SLi,there is finally no signal transmission; i.e., this so-called guardperiod is unassigned in order to have a safety time gap between theindividual time slots which are transmitted in chronological succession.As a result, in particular, disruptive signal superimpositions orinterference between successive slots as a result of signal transit timedifferences such as, for example, in the case of multi path propagation,are substantially avoided so that satisfactory signal detection islargely ensured. Considered overall, the radio transmission of aso-called burst with predefined chronological division or sectioningtherefore can take place during the respective time slot. Detailedinformation on the time frame structure and time slot structure aregiven in the respective mobile radio standard, particularly in the UMTSstandard here with respect to the exemplary embodiment; for example, 3GTS 25.221 “physical channels and mapping of transport channels ontophysical channels (TDD)”, version 3.2.0 (2000–03), 3G TS 25.305 “stage 2functional specification of location services in UTRAN”, Version 3.1.0(2000–03, 3G TS 25.224 “physical layer procedures (TDD)”, Version 3.2.0(2000–03).

In the exemplary embodiment here, the signaling code PS1 of one of theposition elements such as, for example, PE11 is transmitted, by way ofexample, during the time section DA1 in the time slot SLi of the timeframe FRi, given that a free signal section is available.

The localization method which is described, by way of example, but withreference to a UMTS radio communication system also can, of course, beapplied in other radio communication systems such as, for example, onesaccording to the GPRS (General Packet Radio Service), or EDGE (EnhancedData Rates for GSM Environments) standard.

Although the present invention has been described with reference tospecific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the present invention as set forth in the hereafter appended claims.

1. A method for determining a position of at least one subscriber deviceof a radio communication system which has a plurality of base stations,each base station supplying an associated radio cell via at least oneair interface, the method comprising the steps of: providing one or moreradio cells with one or more position elements; transmitting at leastone locating measuring signal by at least one position element from atleast one radio cell which is adjacent to a radio cell in which asubscriber device to be located is present and in which too few or noposition elements are present; and using the at least one locatingmeasuring signal of the at least one adjacent radio cell having one ormore position elements to determine the position of the subscriberdevice in the radio cell in which the subscriber device is located at acurrent point in time.
 2. A method for determining a position of atleast one subscriber device of a radio communication system as claimedin claim 1, wherein signaling on an air interface of the base station ofthe radio cell in which the subscriber device is located is effectedusing a time-division multiplex method.
 3. A method for determining aposition of at least one subscriber device of a radio communicationsystem as claimed in claim 2, wherein the time-divisional multiplexmethod is a time division duplex mode of a Universal MobileTelecommunications System standard.
 4. A method for determining aposition of at least one subscriber device of a radio communicationsystem as claimed in claim 1, the method further comprising the step ofassigning a unique identification code to the at least one locatingmeasuring signal.
 5. A method for determining a position of at least onesubscriber device of a radio communication system as claimed in claim 1,wherein the subscriber device is a mobile telephone.
 6. A method fordetermining a position of at least one subscriber device of a radiocommunication system as claimed in claim 1, wherein the at least onelocating measuring signal is transmitted, during at least one unoccupiedsignal section, into at least one of signaling traffic of a base stationof an assigned radio cell for the at least one position element andsignaling traffic of a base station of the radio cell in which thesubscriber device is located.
 7. A method for determining a position ofat least one subscriber device of a radio communication system asclaimed in claim 1, wherein the at least one locating measuring signalis transmitted, during a specially inserted quiescent time, into atleast one of signaling traffic of a base station of an assigned radiocell for the at least one position element and signaling traffic of abase station of the radio cell in which the subscriber device islocated.
 8. A method for determining a position of at least onesubscriber device of a radio communication system as claimed in claim 1,wherein locating measuring signals of at least two position elements areused for determining the position of the subscriber device to belocated.
 9. A method for determining a position of at least onesubscriber device of a radio communication system as claimed in claim 8,the method further comprising the step of synchronizing the at least twoposition elements with respect to a timing pattern of radio signaling onan air interface of a base station of the radio cell in which thesubscriber device is located.
 10. A method for determining a position ofat least one subscriber device of a radio communication system asclaimed in claim 1, the method further comprising the step ofdetermining and making available for evaluation a transit time of thelocating measuring signal for its transit path between its respectiveposition element and the subscriber device to be located.
 11. A systemfor determining a position of at least one subscriber device of a radiocommunications system, comprising: a plurality of base stationsassociated with a respective plurality of radio cells; at least onesubscriber device, of the radio communication system, which is to belocated; at least one position element for transmitting at least onelocating measuring signal from at least one radio cell which is adjacentto a radio cell in which the subscriber device to be located is presentand in which too few or no position elements are present; and a devicefor using the at least one locating measuring signal of the at least oneadjacent radio cell having one or more position elements to determinethe position of the subscriber device in the radio cell in which thesubscriber device is located at a current point in time.
 12. A systemfor determining a position of at least one subscriber device of a radiocommunication system as claimed in claim 11, wherein the device forusing the at least one locating measuring signal to determine theposition of the subscriber device is connected to a base station of theradio cell in which the subscriber device is located.
 13. A device fordetermining a position of at least one subscriber device of a radiocommunication system as claimed in claim 11, wherein the device forusing the at least one locating measuring signal to determine theposition of the subscriber device is incorporated into a base station inthe radio cell in which the subscriber device is located.
 14. A systemfor determining a position of at least one subscriber device of a radiocommunication system as claimed in claim 11, wherein the device forusing the at least one locating measuring signal to determine theposition of the subscriber device is incorporated in the subscriberdevice to be located.